Retractable safety belts

ABSTRACT

Retractable safety belt apparatus in which a strap is extended from a reel to a selected length and in which the apparatus is thereafter locked automatically to prevent further extension of the strap. Disclosed are: various mechanisms for controlling the operation of the extension-preventing device, including mechanisms driven by the reel and mechanisms responsive to strap tension; different types of strap clamps which open automatically during retraction of the strap and close automatically after desired extension of the strap; mechanisms which facilitate retraction of the strap; a mechanism which temporarily disables the extension-preventing device to permit the user to lengthen the belt after it has been fastened; and a belt fastener which ensures that the extended strap will always retract a bit after the belt is fastened.

Board et al.

[111 3,817,473 [45'] June 18,1974

[ RETRACTABLE SAFETY BELTS [76] Inventors: Richard G. Board, 3000 Conn Ave, Washington, DC. 20008; Nelson H. Shapiro, 640 Washington Bldg, Washington, DC. 20005 22 Filed: -N0v.5, 1964 21 Appl. No.: 409,266

[52] US. Cl 242/107.2, 242/107 S B, 297/388 [51] Int. Cl A62b 35/00 [58] Field of Search... 297/388; 242/107 SB, 107.4, 242/l07.2, 107.3; 188/65.1; 280/150 SB;

[56] v References Cited UNITED STATES PATENTS 1,569,699 l/l926 Bergstrom et al. 242/l07.2 2,947,353 8/1960 Von Wimmersperg 207/385 3,174.704 3/1964 Replogle...; 242/l07.4

7/1965 Roe 297/385 Primary ExaminerWerner H. Schroeder Attorney, Agent, or Firm-Shapiro and Shapiro [5 7] ABSTRACT Retractable safety belt apparatus in which a strap is extended from a reel to a selected length and in which the apparatus is thereafter locked automatically to prevent further extension of the strap. Disclosed are: various mechanisms for controlling the operation of the extension-preventing device, including mechanisms driven by the reel and mechanisms responsive to strap tension; different types of strap clamps which open automatically during retraction of the strap and close automatically after desired extension of the strap; mechanisms which facilitate retraction of the strap; a mechanismwhichtemporarily disables the extension-preventing device to permit the user to lengthen the belt after it has been fastened; and a belt fastener which ensures that the extended strap will always retract a bit after the belt is fastened.

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ATTORNEYS PMUWEUJUW 18 1914 INVENTORS RICHARD 6. BOARD NELSON H. SHAPIRO BY 56 cpl/0 212d 6a u'm ATTORNEYS PATENTEUJUII 1a m sum 11 or 15 INVEN TOR 5 I RICHARD G-BOARD NELSON H. SHAPIRO BY Shapiro 06! 70 ATTORNEYS t mm I 8. m4

SHEET 120% 15 INVENTOR 5 RICHARD 6. BOARD NELSON H. SHAPIRO.

ATTORNEYS PATENTEDJun a mu sum 13 w 15 INVENTORS RICHARD G.'BOARD NELSON H. SHAPIRO mm W .m o 5 d m .m M 5 w mm w 1914 v 3; 8 if; saw '1 [W15 FIG". 45

1 7 CENTRIFUGAL 62 e4 RICHARD G. BOARD CLUTCH NELSON H. SHAPIRO BY S/Zcz/aira Cl la 1 0 ATTORNEYS INVENTORSY PAWNIEMN I e um FIG. 49

- INVENTORS RICHARD G. BOARD NELSON H. SHAPIRO BY Ska Dire and 9mm ATTORNEYS 1 RETRACTABLE SAFETYBELTS This invention relates to retractable safety belts and more particularly to so-called retractable seat belts for use in automotive vehicles. Copending application Ser. No. 377,344, filed June 23,-l964 for Retractable Safety Belts, now Pat. No. 3,289,970, granted Dec. 6, I966, discloses and claims retractable seat belt apparatus in which a strap having a fastener member at a free end thereof may be grasped by the user and extended from a retraction device to placethe strap in user-restraining position, whereupon further extension of the strap is prevented automatically in response, for example, to the cessation of extensile movement or to slight retractile movement of the strap. .At the user-restraining position the strap may have any selected length within a wide range of lengths, so as to accommodate varying conditions of user size and clothing. The fastener member is engaged with a mating fastener member in order to complete the belt. When the fastener members are disengaged, the strapretracts automatically. The present application discloses and claims improvements and modifications in such apparatus and discloses and claims related apparatus.

It is accordingly a principal object of the invention to provide improved retractable seat belt apparatus and the like.

-Another object of the invention is to provide improved retractable seat belt apparatus in which a strap may be readily extended to any selected length within a wide range of lengths, locked automatically against further extension, and retracted automatically when released.

A further object of the invention is to provide improved apparatus for clamping and for controlling the clamping of a strap and the like.

Another object of the invention is to provide improved apparatus for holding a clamp open during extension of a strap to a desired length and for automatically permitting the clamp to close thereafter.

Still another object of the invention is to provide improved apparatus for retractable seat belts and the like which is responsive to changes in tension of a strap.

Another object of the invention is to provide improved apparatus for facilitating retractile movement of a strap through a clamp which prevents extensile movement.

Yet another object of the invention is to provide improved apparatus for ensuring some retraction of a strap after extension thereof to a selected length in order to condition a strap clamp to prevent further extension of the strap.

An additional object of the invention is to provide improved retractable seat belt apparatus and the like employing a clamp of the type in which a strap is wound about a clamping pin for exerting a force thereon to clamp the strap in response to an extensile pull.

Still another object of the invention is to provide, in apparatus of the foregoing type, improved means for holding the clamping pin in an open position during extension of the strap to a desired length.

A further object of the invention is to provide retractable seat belt apparatus which is normally locked against extension when in user-restraining position but which incorporates means for permitting extension without unfastening the belt, while preventing retrac- An additional object of the invention is to provide apparatus of the foregoing type requiring only aspring for moving the clamp to its open position when the strap is retracted.

Still another object of the invention is to provide retractable seat belt apparatus of the foregoing type which utilizes variations in the forces in the strap extending from the clamping pin to provide the desired locking action.

Yet another object of the invention is to provide improved retractable seat belt apparatus and the like employing a feeler mechanism for sensing the amount of strap wound upon a retraction reel and for controlling a strap clamp accordingly.

Still another object of the invention is to provide retractableseat belt apparatus employing a sector driven by a retraction reel for controlling the operation of a strap clamp.

A still further object of the invention is to provide retractable seat belt apparatus in which a relatively small pivotal movement of a strap clamp is sufficient to place the clamp in open or closed position.

An additional object of the invention is to provide retractable seat belt apparatus and the like employing improved pivoting or sliding clamp apparatus.

A still further object of the invention is to provide, in retractable seat belt apparatus and the like, improved means for reducing undesired friction in the movement of a strap past a clamp element.

To summarize briefly, and without intent to limit the scope of the invention, a preferred embodiment of the invention employs in conjunction with a retraction reel, a strap clamp'which moves automatically to an open position when the strap is retracted, which remains in that position when the strap is extended to a desired length, and which thereafter moves automatically to a closed position at which extension is prevented, the strap retracting automatically when unfastened.

The foregoing and other objects, advantages, and features of the invention, and the manner in which the same are accomplished will become more readily apparent upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings, which illustrate preferred and exemplary embodiments, and wherein:

FIG. 1 is a perspective view illustrating the external appearance of housing, strap, and fastener components of a typical embodiment of retractable seat belt apparatus in accordance with the invention;

FIG. 2 is a plan view illustrating one embodiment of apparatus which may be contained within the housing shown in FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 4A is a similar sectional view illustrating still another condition of the apparatus;

FIG. 5 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 6 is a sectional view taken along line 66 of FIG. 5;

FIG. 7 is a similar sectional view illustrating another condition of the apparatus;

FIG. 8 is a plan view illustrating another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 9 is a sectional view taken along line 99 of FIG. 8;

FIG. 10 is a similar sectional view illustrating another condition of the apparatus;

FIG. 11 is a similar sectional view illustrating a modification;

FIG. I2 is a perspective view of a detail of the apparatus of FIGS. 8 11;

FIG. I3 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 14 is a sectional view taken along line 14 14 of FIG. 13:

FIG. 15 is a similar sectional view illustrating another condition of the apparatus;

FIG. 16 is a similar sectional view illustrating still another condition of the apparatus;

FIG. 17 is a sectional view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 18 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 19 is an elevation view, partly in section, illustrating improved fastener apparatus which may be employed in the invention;

FIG. 20 is a plan view, partly in section, of the apparatus of FIG. 19;

FIG. 21 is a sectional view of a detail of strap clamping apparatus in accordance with one concept of the invention;

FIG. 22 is a plan view of the apparatus of FIG. 21;

FIG. 23 is asectional view of a modified form of clamp apparatus;

FIG. 24 is a sectional view of still another form of clamp apparatus;

FIG. 25 is a sectional view of yet another form of clamp apparatus.

FIG. 26 is a plan view of still another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 27 is a sectional view taken along line 27 27 of FIG. 26;

FIG. 28 is a similar sectional view illustrating another condition of the apparatus;

FIG. 29 is a similar sectional view illustrating still another condition of the apparatus;

FIG. 30 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 31 is a sectional view taken along line 31 31 of FIG. 30;

FIG. 32 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 33 is a sectional view taken along the line 33-33 of FIG. 32;

FIG. 34 is a similar sectional view illustrating another condition of the apparatus;

FIG. 35 is a sectional view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 36 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 37 is a sectional view of a modified form of apparatus which may be contained within the housing of FIG. 1;

FIG. 38 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 39 is a sectional view taken along line 39 39 of FIG. 38;

FIG. 40 is a similar sectional view illustrating another condition of the apparatus;

FIG. 41 is a similar sectional view illustrating still another condition of the apparatus;

FIG. 42 is a sectional view of another embodiment of apparatus which may be contained within the housing of FIG. 1;

FIG. 43 isa similar sectional view illustrating another condition of the apparatus;

FIG. 44 is a sectional view of another embodiment of the apparatus which may be contained within the housing of FIG. 1; I

FIG. 45 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 46 is a plan view of a modification of the apparatus of FIG. 2;

FIG. 47 is a plan view of still another modification of the apparatus of FIG. 2;

FIG. 48 is a sectional view taken along line 48 48 of FIG. 47; and

FIG. 49 is a similar sectional view illustrating another condition of the apparatus.

Referring to the drawings, as shown in FIG. 1 a retractable seat belt of the invention may comprise a strap 10 of suitable material, such as nylon webbing, adapted to be extended from a housing 12 and to be retracted into the housing. The housing may be supported upon the floor of a vehicle, in any convenient orientation, at one side of a seat, or if the seat is strongly anchored to the floor, the housing may be supported directly upon the seat. A free end of strap 10 is provided with a fastener member 14, which in the form shown, is a conventional tongue having locking openings 16. The tongue is adapted to engage a mating fastener member 18, such as a conventional buckle into which the tongue is inserted to complete the belt. As is well known in the art, when the tongue is inserted into the buckle, locking abutments of the buckle enter the openings 16 of the tongue to retain the fastener members in locked engagement until a release element, such as a pivoting lever 20, is operated. Buckle 18 may be connected to another strap, 22, the remote end of which (not shown) may be anchored to the floor (or to the seat) at the opposite side of the seat. Under appropriate circumstances strap 22 may be dispensed with and the mating fastener member 18 may be supported directly upon the seat or otherwise anchored to the floor.

In accordance with the invention it is desired that the strap 10 be readily extensible from the housing 12 to place the strap in user-restraining position, then be locked against further extension automatically, and Finally be retracted into the housing when released. Moreover, it is desired that strap be capable of extension to any desired length within a wide range of lengths, so that all adjustments in length to accommodate different size users and different clothing conditions may be made by the strap 10. Strap 22 may then be kept very short or may be eliminated as indicated above.

FIGS. 2, 3, 4 and 4A illustrate one embodiment of an apparatus'which may be employed in the housing 12 in order to accomplish the foregoing purposes. As shown in FIG. 2, a frame comprising a pair of side plates 24 and 26 supports a retraction reel 28. The frame may be secured to or form part of the housing and should be anchored to the floor or, under appropriate circumstances, to the seat. The reel comprises a pair of end discs 30 and 32 joined by a sleeve hub 34, the end discs being provided'with suitable bearings, as is well known in the art, for rotatably supporting the reel upon a pin 36 which extends through the sleeve hub with substantial space therebetween. A spring motor for winding the reel may comprise a helical torsion spring 38 which is slipped over the pin 36 with substantial free play. One end of the spring may be secured to an end disc or the sleeve hub and the other end tothe pin 36, so that the spring is wound as the reel is turned relative to the 'pin. Other well known types of retracting reels may also be employed.

Strap 10 has the end remote from fastener member 14 attached to the hub of the reel so that the strap may be wound upon the reel by the reel spring for retraction and may be extended from the reel while'winding the spring. In the form shown the strap is trained from the bottom of the reel.

In order to prevent extension of the strap a clamp 40 is employed. In the form shown the clamp comprises a convexly contoured clamping plate 42 supported by a cross bar 44 between the side plates 24 and 26. Plate 42 has a pair of side members 46 which along with plate 7 42 constitute a yoke for supporting a pivoting clamp member 48. Clamp member 48 is supported upon a pin 50 extending between the side members. A'torsion spring 52 received within a bore at one end of the pivoting clamp member, and having its respective ends connected to one of the side members 46 and to the clamp member, biases the clamp member toward a position at which a clamping surface 54 engages the strap 10 as shown in FIG. 4A. The clamping surface may be roughened, knurled, or longitudinally grooved so as to facilitate the clamping action, as well known in the art. Clamping surface 54 is shaped so as to increase the clamping pressure in response to extensile strap pull. This is accomplished by suitably shaping the clamping surface, as by making the trailing edge of the clamping surface a greater distance from the pivot 50 than the to permit the strap tobe retracted even when the clamp has moved to the closed position shown in FIG. 4A. This action is facilitated by contouring the teeth or corrugations of the clamping surface so that they are inclined rearwardly for ready engagement with the strap when the strap is extended but to minimize engagement when the strap is retracted.

In order to open the clamp so that the strap may be extended to the desired length a feeler 56 is employed for sensing the amount of strap wound upon the reel. In the form shown the feeler comprises a lever arm extending from the pivoting clamp element 48, being secured to the top thereof by a small block 58. It will be seen that when the reel is sufficiently filled the strap thereon engages the free end of the feeler and lifts the feeler so as to turn the clamp member 48 to open it as shown in FIG. 3. When the strap is sufficiently extended from the reel, the feeler is free of the strap as shown in FIG. 4A, and the clamp is permitted to close. The feeler may be shaped so as to engage the strap wound upon the reel within a predetermined range of wound strap. For example, the feeler may engage the strap until the strap has been withdrawn from the reel about eighteen inches and then be free of the strap.

The feeler opens the clamp to permit initial extension of the strap but will not maintain the clamp open after initial extension. In order to maintain the clamp open until the strap has been extended approximately to its user-restraining length an additional mechanism is employed. In the form shown this mechanism comprises one ormore sectors 60, 62 driven by the reel. The sectors are pivotally supported by stub shafts 64 upon the side plates of the frame and engage the periphery of the end discs of the reel, which may be provided with rubber O-rings 66 preferably seated in grooves on the peripheral surface of the end discs. The sectors are connected by a pin 68, so that they move in unison and are provided with a tension bias spring 70, one end of which may be connected by a screw to the top of one sector and the other end of which may be connected by a screw to the block 58.

When the strap is extended, the reel turns counterclockwise as shown in FIG. 4, lifting the sectors and engaging pin 68 with the undersurface of the feeler in order to hold the clamp open even after the feeler loses contact with the webbing. At this position the lower edge of the sector surface is just maintained in contact with the reel, presenting a slight drag on the reel. The strap is extended to approximately the desired length, andthe tongue 14 (FIG. 1) is engaged with the buckle 18. In so doing it is almost impossible to avoid extending the strap slightly more than the length required when the tongue and buckle are later snugly against the users body. Thus, after the tongue is engaged with the buckle, strap 10 is always retracted slightly, the reel turning in a retractile direction, clockwise in FIG. 4A. When this occurs, the sectors turn away from the feeler, permitting the clamp to-close. Any further extensile movement of the strap is now prevented. As shown in FIG. 4A the sectors may actually lose contact with the reel by a slight amount and come to rest upon the supporting bar 44, the tension in bias spring 70 being negligible at this time. Thus, in a collision, even if the strap were to slip slightly through the clamp before the clamp engaged firmly there would be no possibility of the sectors being driven by the reel to open the clamp.

If now the tongue is disengaged from the buckle, the reel retracts the strap, dragging it through the clamp, which opens slightly due to the retractile movement, and eventually the feeler 56 engages the strap as shown in FIG. 3, turning the clamp element 48 clockwise in that figure to open the clamp more fully. This turning movement of the clamp element increases the tension in bias spring 70 enough to engage the upper edge of the sectors with the reel, but the drag on the reel is minimal. When the strap is extended again, the sectors are immediately raised to the position of FIG. 4.

The amount of retractile movement of strap 10 required to permit the clamp to close is very slight, of the order of H4 inch, and depends upon how much webbing remains on the reel and the relative radii of the reel and the sectors. The mechanical advantage of the feeler and the sectors determines the back pressure upon the reel, which has been found to be quite low. By utilizing a roller at the end of the feeler engaging the strap, as will be later described, the drag upon the reel created by the feeler is further reduced.

FIGS. 47 49 illustrate a modification in which the clamp is additionally opened when a strap is retracted a predetermined amount so as to facilitate flow of the strap through the clamp during further retraction. As shown, this may be accomplished by providing additional sectors 69 driven by the reel. These sectors are supported on stub shafts 71 from the side plates of the frame and have a bail 72 pivotally suspended therefrom at the side of the stub shafts remote from the reel. While the strap is being extended, the sectors 69 are in the full line position of FIG. 49, and there is substantial space between the bail 72 and the feeler. The slight retractile movement of the strap required to permit the clamp to close is not sufficient to engage the bail with the feeler, the sectors 69 moving to the phantom line position. However, further retractile movement causes the bail to lift the feeler very slightly but enough to facilitate the retractile movement of the strap through the clamp. If the strap is permitted to retract sufficiently to engage the bail 72 with the feeler and then is pulled again in an extensile direction, the slight extensile tuming movement of the reel will disengage bail 72 from the feeler and permit the clamp to close instantly. The lifting movement of the feeler by the bail 72 is preferably made insufficient to create enough tension in bias spring 70 to engage sectors 60 and 62 with the reel. The relative degrees of rotation of the pairs of sectors may be controlled by varying their radii and/or by engaging the pairs of sectors with different diameter portions of the reel; the end discs may be stepped down accordingly to provide shoulders for engaging the respective pairs of sectors.

FIGS. 19 and 20 illustrate the manner in which strap fastener members may be modified to ensure sufficient retraction of the strap to operate the clamp of a retraction-responsive apparatus. As shown, either or both parts of the fastener couple may be constructed so as to provide lost motion. Thus the tongue fastener member 14A may have a shell 73 into which the tongue proper 74 may telescope. The shell is attached to the strap 10 and the tongue is normally urged out of the shell, as by compression springs 76. Thus if the tongue is inserted in a conventional buckle, the resistance to insertion created by the latch members of the buckle will cause the shell 73 to telescope about the tongue 74 before the tongue is forced into the buckle. After the tongue has been engaged with the buckle, the shell will be free to move in the reverse direction under the bias of springs 76 to create some slack in the strap 10, which will be taken up by the retraction reel.

The same type of telescoping action may take place in the buckle 18A. When atongue is inserted into the opening 78, the latch abutment 80 will retreat along the buckle shell along with the release lever 82, the pivots 84 of which slide in slots 86 in the sides of the buckle shell as a spring 88 is compressed. Finally the insertion pressure exerted by the tongue will be sufficient to turn the abutment 80 upward against its usual bias spring, not shown, to permit the tongue to slip under the abutment so that the abutment may enter the opening in the tongue. Then the tongue is moved reversely by spring 88 so as to create slack in strap 10 which is taken up by the retraction reel. Other types of lost motion fastener members may also be employed to create slack to be retracted.

FIG. 46 illustrates a modification of the apparatus of FIG. 2 in which the end discs of the reel are split into two parts 30A, 30B, and 32A, 32B. The B parts are fixed to the hub of the reel and turn integrally therewith, while the A parts are coupled to the B parts by centrifugal clutches contained within the end discs. The clutches may be.of any conventional type well known in the art for coupling a pair of rotary members when one of them is turned and for decoupling the members when that one stops. Under these circumstances the sectors 60 and 62 will not move up to engage the feeler 56.until the reel proper has turned somewhat, the feeler 56 holding the clamp open until the sectors take over this function. When the reel ceases its extensile movement, the disc portions 30A and 32A will be decoupled therefrom, so that the pressure of the feeler upon the sectors, due to the bias spring 52 of the clamp, will permit the sectors to move down, turning the disc portions 30A and 32A relative to the reel and closing the clamp without requiring retractile movement of the strap.

FIGS. 5, 6, and 7 illustrate another embodiment of the apparatus which may be placed in housing 12 of FIG. 1. A retraction reel 90, which may be of the type previously described, is rotatably supported upon a frame 92. The strap 10 extends from the bottom of the reel past a clamp 94 comprising a fixed clamp plate or block 96 and a pivoting clamp element 98. Element 98 is pivotally supported at one side of a shaft 100 extending between the side plates of the frame and has a lever arm 102 at the opposite side of shaft 100 supporting a strap guide roller 104 arranged to indent the strap. Guide rollers 106, and 108 are rotatably supported upon the frame at opposite sides of roller 104, so that the strap passes reversely about roller 104. An additional guide roller 110 may be provided to guide the strap across the fixed clamp element 96.

When the strap is extended, the resulting tension in the strap exerts a pressure on roller 104 and turns lever arm 102 so as to bring the clamping surface 112 of clamp element 98 into engagement with the strap, overcoming a return spring 114, which maintains the clamping surface 112 away from the strap when there is reduced tension in the strap.

A feeler 116 is pivotally supported by a pin 118 upon the frame and has an arm 120 arranged to interfere with the movement of clamp member 98 when sufficient strap is wound upon the reel. As shown, the free 

1. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, a support past which said strap is trained, clamp means for clamping said strap to said support, and means for sensing the strap wound upon said reel and for opening said clamp means when a predetermined amount of strap is wound upon said reel.
 2. The retractable seat belt of claim 1, said sensing means comprising a feeler engaged by the strap wound upon said reel when a predetermined amount of strap is wound upon said reel, said feeler being operatively coupled to said clamp means.
 3. A retractable belt or the like comprising a retraction reel, a strap connected to said reel for retraction and extension, means for clamping said strap and preventing extension thereof, and feeler means for sensing the amount of strap wound upon said reel and for opening said clamp means when a predetermined amount of strap has been retracted.
 4. The retractable belt of claim 3, further comprising means responsive to a change in tension in said strap for closing said clamp means.
 5. A retractable seat belt or the like comprising a spring-wound retraction reel, a strap connected to said reel for retraction and extension, clamp means for preventing extension of said strap, direction-changing strap guide means past which said strap is trained for exerting a closing force upon an element of said clamp means proportional to the spring force of said reel during extension of said strap, and means operative only after substantial retraction of said strap to a non-restraining position for maintaining said clamp means open during extension of said strap to a desired length, and for thereafter permitting said clamp means to close, said maintaining means comprising means responsive to the amount of strap wound upon said reel.
 6. A retractable seat belt or the like comprising a spring-wound retraction reel, a strap cOnnected to said reel for retraction and extension, clamp means for preventing extension of said strap, direction-changing strap guide means past which said strap is trained for exerting a closing force upon an element of said clamp means proportional to the spring force of said reel during extension of said strap, and means operative only after substantial retraction of said strap to a non-restraining position for maintaining said clamp means open during extension of said strap to a desired length, and for thereafter permitting said clamp means to close, said maintaining means comprising feeler means engaging the strap wound upon said reel for holding said clamp means open when a predetermined amount of strap is wound upon said reel.
 7. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, a support adjacent to said reel, a pivoting clamp for clamping said strap to said support, said clamp having an actuating arm with a strap guide indenting said strap, said strap being trained over said guide in a direction to exert a clamp-closing force upon said arm in response to strap tension, means for opening said clamp in the absence of a substantial amount of tension in said strap, and feeler means for sensing the amount of strap wound upon said reel and for preventing the closing of said clamp when a predetermined amount of strap is wound upon said reel.
 8. The retractable seat belt of claim 7 said feeler means comprising an arm positioned to prevent closing movement of said clamp when said predetermined amount of strap is wound upon said reel, and means for urging said arm away from its closing movement preventing position.
 9. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, a support adjacent to said reel and past which said strap is trained, a clamp member supported for pivotal movement toward and away from said support, a lever arm connected to said clamp member and having a strap guide adapted to indent said strap, spring means for turning said clamp member to an open position away from said support and for causing said guide to indent said strap, a feeler pivotally supported adjacent to said reel and having an element for sensing the strap wound upon said reel and an arm positioned to interfere with the pivotal movement of said clamp member toward said support when a predetermined amount of strap is wound upon said reel, and spring means for moving said arm away from the position at which it interferes with said clamp member movement toward said support.
 10. A retractable seat belt comprising retraction means, a strap connected to said retraction means for retraction and extension, clamp means for preventing extension of said strap, said clamp means comprising a pair of clamp elements, one of said elements being movable relative to the other, said strap being trained from said retraction means around said one element for exerting a force upon said one element tending to move said one element toward or away from said other element depending upon the position of said one element relative to the other, means for moving said one element to a position away from said other element when said strap has been retracted a predetermined amount, and means responsive to an extensile pull upon said strap for maintaining said one element in the last-mentioned position while said strap is extending to a selected length and responsive to reduction of said pull for moving said one element toward said other element.
 11. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, a clamp having a pair of clamp elements, one of said elements being movable relative to the other, said strap being trained from said reel between said clamp elements and around said one element, whereby said strap may exert a force upon said one element tending to move said one element toward or away from said other element, Said clamp being pivotally supported for movement between a pair of positions at which said clamp elements are respectively apart or together corresponding to open and closed positions of the clamp, means for moving said clamp to said open position when said strap is retracted, and means for maintaining said clamp in said open position in response to tension in said strap during extension of said strap to a desired length and for thereafter permitting said clamp to move to said closed position.
 12. A retractable seat belt comprising retraction means, a strap connected to said retraction means for retraction and extension, a clamp for clamping said strap and preventing extension thereof, said clamp comprising a pair of clamp elements, at least one of said elements being supported for pivotal movement and for movement toward and away from the other of said elements, means for moving said one element to a position away from said other element when said strap is retracted, at which position said one element is located at one side of the axis of its pivotal movement, means for maintaining said one element at said position while said strap is extended to a desired length, and means responsive to the cessation of the extension of said strap to said desired length for causing said one element to move to a position at the opposite side of said pivotal axis and to move toward said other element for clamping said strap.
 13. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, clamp means for preventing extension of said strap, said clamp means comprising a pair of clamp elements, one of said elements being movable toward and away from the other of said elements and both of said elements being supported for pivotal movement about an axis substantially parallel to the rotational axis of said retraction reel, said strap being trained from said reel between said elements and around said one element reversely whereby said strap may exert a force upon said one element for controlling its movement relative to said other element and for controlling the pivotal movement of said elements, means for moving said elements about said pivotal axis to a position at the side of said axis remote from said reel when said strap is retracted, means responsive to the tension in said strap during extension of said strap to a desired length for maintaining said elements in said position, and means responsive to the reduction of said tension when said strap has reached said length for causing said elements to move about said pivotal axis to the side thereof adjacent to said reel and for causing said one element to move toward said other element for clamping said strap.
 14. The retractable seat belt of claim 13, said first-mentioned moving means comprising means for sensing the amount of strap wound upon said reel.
 15. The apparatus of claim 13, said first-mentioned moving means comprising a bias spring.
 16. The retractable seat belt of claim 13, said first-mentioned moving means comprising a bias spring for moving said elements part way to the first-mentioned position and means responsive to the amount of strap wound upon said reel for moving said elements the remainder of the way to said position.
 17. The retractable seat belt of claim 13, said strap being trained from said reel at the side thereof which produces a minimum angle between the portions of the strap passing around said one element when said elements are in the first-mentioned position and an increasing angle as said strap is extended from said reel.
 18. The retractable seat belt of claim 13, further comprising strap guide means for minimizing the variation in angle of the strap portion extending from said first element remote from said reel.
 19. The retractable seat belt of claim 13, said means for maintaining said elements at the first-mentioned position comprising stop means for limiting the pivotal movement of said elements.
 20. A retractable seat belt comPrising retraction means, a strap connected to said retraction means for retraction and extension, clamp means for clamping said strap and preventing extension thereof, said clamp means comprising a pair of clamp elements, one of said elements comprising a pin supported for reciprocation toward and away from the other of said elements, said strap being trained between said elements and around said one element reversely, and means for pivotally supporting said clamp means for movement between a closed position and an open position, said strap having an orientation with respect to said one element in said closed position at which the tension in said strap urges said one element toward said other element and having an orientation with respect to said one element in said open position at which the tension in said strap urges said one element away from said other element.
 21. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, clamp means for preventing extension of said strap, said clamp means comprising a pair of clamp elements, one of said elements being movable toward and away from the other of said elements, said clamp means being supported for pivotal movement about an axis substantially parallel to the rotational axis of said retraction reel, said strap being trained from said reel between said elements and around said one element, means for moving said clamp means about said pivotal axis to an open position at which said elements are apart when said strap is retracted, and means for maintaining said clamp means in said position during extension of said strap to a desired length, and for thereafter permitting said clamp means to move about said pivotal axis to a closed position at which said elements are together.
 22. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, clamp means for preventing extension of said strap, said clamp means comprising a pair of clamp elements, one of said elements being supported for movement toward and away from the other of said elements, said strap being trained from said reel between said elements and reversely around said one element whereby said strap may exert a force upon said one element, at least said one element being pivotally movable between a first position adjacent to said reel, at which said clamp means is closed, and a second position remote from said reel, at which said clamp means is open, said strap having an orientation with respect to said one element and the axis of pivotal movement of said one element which, at said second position produces a resultant force upon said one element which maintains said one element at said second position when said strap is retracted and during extension of said strap to a desired length and which produces a resultant force which moves said one element to said first position when said strap has been extended to said length.
 23. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, clamp means for preventing extension of said strap, means for pivotally supporting said clamp means for movement between a first position at which said clamp means is closed and a second position at which said clamp is open, and means responsive to the amount of strap wound upon said reel for pivotally moving said clamp means to said second position.
 24. A retractable seat belt comprising retraction means, a strap connected to said retraction means for retraction and extension, clamp means for clamping said strap and preventing extension thereof, said clamp means comprising a pair of clamp elements, one of said elements comprising a pin supported for reciprocation toward and away from the other of said elements, said strap being trained between said elements and around said one element reversely, means for pivotally supporting said clamp means for movement between a closed position and an open position, said stRap having an orientation with respect to said one element in said closed position at which the tension in said strap urges said one element toward said other element and having an orientation with respect to said one element in said open position at which the tension in said strap urges said one element away from said other element, and spring means for moving said clamp means to said open position when said strap is retracted.
 25. The retractable seat belt of claim 24, said clamp means being supported for pivotal movement through approximately 90* about an axis laterally positioned relative to the reciprocation of said pin.
 26. A retractable seat comprising retraction means, a strap connected to said retraction means for retraction and extension, clamping means for preventing extension of said strap and having a pair of clamp elements one of which is movable toward and away from the other for closing and opening said clamping means, and means for supporting said clamping means for pivotal movement about an axis between closed and open positions, said strap being trained from said retraction means reversely about said one clamp element to a fastener end and being oriented to pull said one element toward said other element and away from said pivotal axis in response to extensile pull at said fastener end when said clamping means is in said closed position.
 27. A retractable seat belt or the like comprising retraction means, a strap connected to said retraction means for retraction and extension, a strap guide past which said strap is trained from said retraction means for exerting a force on the guide, means for preventing extension of said strap, means operative only after substantial retraction of said strap to a non-restraining position for disabling said extension-preventing means during extension of said strap to a restraining position and for thereafter responding to a change in said force to enable said extention-preventing means to operate said extension-preventing means comprising a fixed part and a movable part constituting said guide, said disabling means comprising means for pivotally supporting said guide for movement away from said fixed part to a position at which the force on said guide during extension of said strap urges said movable part away from said fixed part.
 28. A retractable seat belt or the like comprising retraction means, a strap connected to said retraction means for retraction and extension, means for clamping said strap to prevent extension, and means operative only after substantial retraction of said strap to a non-restraining position for holding said clamp means open during extension of said strap to a restraining position and for thereafter responding to a change in movement of said strap to enable said clamp means to close.
 29. The retractable seat belt of claim 1, further comprising means reponsive to extensile movement of said reel when said strap is extended therefrom for maintaining said clamp means open until said strap has been extended substantially to a desired length.
 30. The retractable seat belt of claim 29, the last-mentioned means comprising a sector driven by said reel.
 31. The retractable seat belt of claim 2, further comprising sector means driven by said reel, said sector means being positioned to engage said feeler and maintain said clamp means open until said strap has been extended substantially to a desired length.
 32. The retractable seat belt of claim 31, further comprising spring means connected to said sector means and to said clamp means for engaging said sector means with said reel when said clamp means is open and for releasing said sector means from said reel when said clamp means is closed.
 33. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, a support past which said strap is trained, clamp means for clamping said strap to said support in order to prevent extension of said strap, and means driven bY said reel for holding said clamp means open while said strap is being extended to a desired length and for thereafter permitting said clamp means to close.
 34. The retractable seat belt of claim 33, said driven means comprising a sector driven by said reel.
 35. A retractable seat belt or the like as set forth in claim 6, said strap guide means and said element of said clamp means comprising opposite lever arms of a single piece pivotally supported at a fulcrum intermediate said lever arms, said clamp means having another element against which said strap is clamped when the first-mentioned element is turned to close with said other element.
 36. A retractable seat belt or the like as set forth in claim 35, wherein said feeler means comprises a lever pivotally supported independently of said piece and having an arm positioned to engage the strap wound upon said reel and an arm positioned to engage said piece when said predetermined amount of strap is wound upon said reel and to prevent said closing of said one element with said other element.
 37. A retractable seat belt or the like as set forth in claim 6, wherein said feeler means comprises an arm pivotally connected to said element of said clamp means. 